1. Technical Field
The invention includes embodiments that may relate to a system and/or method for monitoring one or more a heat transfer device. The heat transfer device may be in a power plant.
2. Discussion of Art
Power plants may be classified based on the process for electrical power generation. Power plant classifications include thermal power plants, hydroelectric power plants, nuclear power plants, geothermal power plants, wind farms, and solar farms. Each generating modality operates with a specific differing input to produce an electrical power output. In a power plant, a heat transfer device may include a furnace firewall, air preheater, superheater, reheater, economizer, and the like. The heat transfer device may transfer heat from one medium to another medium to maintain a continuous generation of electrical power.
A heat transfer device function may produce an undesired by-product that can subsequently hinder the functioning of the processes. As a result, the efficiency of the power plant decreases with time and overall cost of operation of the power plant increases. Boilers, for example, form an integral part of power plant that uses combustion to generate steam to run turbines. Common types of fuel used to fire boilers include coal and fuel oil. Due to chemical by-products released during combustion, the boilers may foul or form slag.
Fouling is the accumulation of ash and by-products of incomplete combustion as a layer on an inner surface of a boiler. A layer of fouling substance may have low thermal conductivity that reduces the amount of heat transferred in heat exchanging components. In the case of a boiler, this may cause an increase in temperature inside the boiler for a given amount of steam production, a decrease in functional efficiency of the boiler, and an increase in pressure drop within the boiler due to reduced cross-sectional area. Slagging is a process similar to fouling. Slagging refers to deposition of solid or molten layers on the outside surface of the boiler tubes. A process known as sintering may form such layers. Sintering is the bonding of adjacent surfaces of particles into a hard deposit. Sintering subsequently strengthens the mass, causing an increase in tenacity of the deposit on the surface. Both fouling and slagging may be self-propelling processes, meaning that once an initial layer of a material forms on a surface, the layer causes more of the material to be deposited. Sometimes, more heat is requested from the combustion chamber to offset the efficiency loss, and the increased heat production exacerbates the problem.
An air preheater is a heat transfer component in a power plant. The air preheater may transfer heat from re-circulating flue gases to air. The outgoing flue gases from a combustion process may pre-heat air used in other processes. The pre-heating of air reduces the amount of energy spent in raising the temperature of an otherwise cold air to a desired temperature level. Because these flue gases contain organic and inorganic chemicals, the flue gases react with metal tubes disposed within the air preheater and cause corrosion and fouling.
Due to effects as described above, performance of these components drops over time and breaks down or forces a servicing outage. Addition of chemicals to the fuel and treating the device surface is a way of reducing the effects of fouling and slagging. The addition of chemicals may be undesirable. The existing systems that monitor boilers may have a reactive warning system. This means that the systems would raise an alarm or warning only when a problem affects the boilers or other a heat transfer device. By the time the alarm is raised, the effects of fouling and slagging may have progressed to a severe stage that leaves system operators with little option other than to shutdown the boiler for cleaning and/or treating the heat transfer surfaces to bring the boiler performance to acceptable limits. Also, such reactive warning systems may be incapable of predicting when a failure of the boiler might occur. In many cases, evaluation relies instead on the operator experience and knowledge of boiler performance to predict an impending failure.
It may be desirable to have a monitoring system that differs from those systems available today. It may be desirable to have a method of monitoring a system that differs from those methods available today.